The liquid crystal display (LCD) is one of the most common types of flat panel displays (FPDs). LCDs are used in notebook or laptop computers and have also become popular in desktop computer monitors. LCDs are lightweight and occupy less space than conventional cathode ray tube (CRT) displays.
The general structure of an LCD consists of a pair of panels including field generating electrodes and polarizers, and a liquid crystal (LC) layer that is positioned between the panels and subject to an electric field generated by the electrodes. Variations in the field strength change the molecular orientation of the LC layer. For example, upon application of an electric field, the molecules of the LC layer align with the field and polarize light passing through the LC layer. A polarized filter positioned over the electrodes blocks the polarized light, creating a dark area. The dark area represents a desired image, such as an alphanumeric character.
It is common that the field generating electrodes include a plurality of pixel electrodes arranged in a matrix and a common electrode. The common electrode and the pixel electrodes may be disposed on different panels. The panel including the pixel electrodes also may include a plurality of switching elements, such as thin film transistors (TFTs). The TFTs are connected to the pixel electrodes and to a plurality of display signal lines, including gate lines extending in rows and data lines extending perpendicular to the gate lines in columns.
A signal controller and voltage generators may be provided on printed circuit boards (PCBs) located out of the panels. In addition, gate driving and data driving integrated circuits (ICs) may be provided on flexible printed circuits (FPCs) disposed between the PCBs and the panels. There may be separate gate and data PCBs and gate and data driving ICs respectively disposed between the panels and the gate and data PCBs.
In operation, the signal controller is supplied with image signals and input control signals for controlling the display of the image signals. On the basis of the received image signals and input control signals, the signal controller provides gate control signals to the gate driving ICs and processed image signals and data control signals to the data driving ICs. In response to the gate control signals, the gate driving ICs supply voltage from the voltage generator to the gate lines, which turn on the switching elements or TFTs. Similarly, in response to the data control signals, the data driving ICs convert image data to analog voltages and apply these data voltages to the data lines. The data voltages are supplied to corresponding pixel electrodes via the turned on switching elements so as to generate the electric fields required for the desired images.
Some LCDs include only the data PCB without the gate PCB. In this case, a plurality of signal lines for signal communication between the gate driving ICs and the signal controller and the voltage generator may be provided on the data FPC films and the panels.
Some LCDs have neither a gate PCB nor a gate FPC film. In this case, the gate driving ICs may be mounted on one of the panels. The data driving ICs also may be mounted on the panel. This design is known as chip-on-glass (COG). As a result of this configuration, the panel includes a plurality of signal lines for interconnection between the gate driving ICs. The data driving ICs mounted on the panel can still receive signals via data FPC films.
As described above, several signal lines are required to transmit various control signals and voltages to the gate and data driving ICs. These signal lines are subject to corrosion by, for example, electrolysis when moisture permeates into the panels. Therefore, there exists a need in the art for a configuration of driving signal lines that minimizes corrosion of same. There also exists a need in the art for a configuration of LCD components and lines that allows for testing of potentially defective gate or data lines.